Optical apparatuses such as digital cinemas and projectors are required to have a lower cost and a power-saving property. Such an optical apparatus has a plurality of laser devices disposed therein as light source modules so as to achieve a necessary optical output. Use of optical coupling members such as optical fibers coupling light from modules in the optical apparatus is one of the factors determining the cost. Therefore, by increasing the optical output of a single module and reducing the number of laser devices in the optical device, the cost required for the optical coupling members can be reduced, and consequently, the cost per oscillation output of the optical apparatus can be lowered. This leads to a demand for a high-output type light source module having a high oscillation output as a single module.
Conventionally, for example, Patent Documents 1, 2 disclose a structure having a plurality of LD elements arranged in a uniaxial direction on the same plane and coupled to a fiber through two kinds of lenses so as to achieve a high optical output. However, since light-emitting points spread in the uniaxial direction (direction parallel to an emitter array), a divergence angle (etendue) of a synthesized optical beam becomes larger in the direction and, when a predetermined number of LD elements is exceeded, an optical coupling loss increases at the time of fiber coupling, causing a problem of reduced light emission efficiency.
Patent Documents 3, 4 disclose a package structure having a plurality of LD elements mounted on side surfaces of a common holding member in a module and thereby improving an optical output. However, since the structure of Patent Documents 3, 4 has the plurality of LD chips held by the one holding member, a distance between LD chips cannot be shortened, and a divergence angle (etendue) of an optical beam becomes larger in the uniaxial direction (the direction between the LD chips), an optical coupling loss increases at the time of fiber coupling, still causing a problem of reduced light emission efficiency.
Patent Document 5 discloses a package structure in which a plurality of LD chips is mounted in a module by using a stepped holding member. However, the stepped holding member makes it difficult to miniaturize a package as a whole.